Carboxyl containing polymers of vinylidene monomers containing at least one terminal CH.sub.2 &lt;group are well known. Such polymers may be homopolymers, or copolymers with other vinylidene monomers, of unsaturated polymerizable carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like. Often copolymers of these acids are cross-linked with small amounts of cross-linking agents, which in the form of their salts absorb large quantities of water or solvents. These materials are normally prepared by polymerization with a free radical catalyst in an organic medium in a closed vessel or autoclave equipment with stirring. During the course of such polymerizations, shortly after the initiation of polymerization, polymer begins to precipitate from the solution as it is formed and flocculates and forms aggregates. This aggregation is generally uncontrolled and interferes with the polymerization reaction by retarding access of monomer to free radicals and contributing to poor removal of heat of polymerization. As a consequence, it is difficult to obtain uniform polymerizations because of the variation and aggregation, which often becomes worse when there is local variation of temperature in different reactor regions and variation of product quantity from lot to lot is obtained. Further, the precipitated polymer forms a slurry in the solvent which becomes extremely thick, results in ineffective mixing, and generally causes extensive fouling on reactor surfaces of polymer build-up. A further problem is that solvent is trapped in the polymers during aggregation and removal of such trapped solvent is time consuming, decreases production rates and makes it difficult to obtain dried carboxyl containing products having less than 500 ppm of residual medium in the polymer product.